Fluid-actuated cryogenic refrigerator



May 30, 1967 F. F. CHELLIS FLUID-ACTUATED CRYOGENIC REFRIGERATOR 5Sheets-Sheet 1 Filed Dec. 5, 1965 JNVLN'IOR Fred F. Chellis Fig.1

Attorney May 30, 1967 F. F. CHELLIS 3,321,926

FLUID-ACTUATED CRYOGENIC REFRIGERATOR Filed Dec. 5, 1965 5 Sheets-Sheet,

Fred F Challis Attorney May 30, 1967 F. F. CHELLIS FLUID-ACTUATEDCRYOGENIC REFRIGERATOR 5 Sheets-Sheet 3 Filed Dec. 5, 1965 Fig. 7 Fig. 8

Fig. 5 Fig. 6

lNV EN'TOR. Fred F CheHis Attorney United States Patent 3,321,926 FLUIDACTUATED CRYOGENIC REFRIGERATUR Fred F. Chellis, Manchester, Mass,assignor to Arthur D. Little, Inc, Qarnbridge, Mass, a corporation ofMassachusetts Filed Dec. 3, 1965, Ser. No. 511,796 Claims. (Cl. 62-6)This invention relates to apparatus for developing low temperaturecryogenic refrigeration, and more particularly to refrigerationapparatus which includes a novel valve system which makes the apparatusself-regulating, and in a preferable form requires no external drivingmeans other than a source of the high-pressure expansible fluid used inthe refrigerator. It further relates to the refrigeration apparatus forproducing net refrigeration in a system in which some of the workextracted from the compressing, cooling, and expanding of a fluid may bein the form of thermal energy, wherein the fluid leaving the system isat a temperature higher than that at which it entered the system.

In United States Patent No. 2,966,035 there is described a refrigerationmethod and apparatus which is directed to a so-called no-work cycle inwhich refrigeration is obtained by removing more sensible heat from asystem than is taken into the system by the refrigerating fluid used. Inoperation, however, both thermal and mechanical energy are delivered bythis cryogenic refrigerator. Although the cycle described in U.S.P.2,966,035 has a been found to be very successful in producingrefrigeration, even as low as K., the method and apparatus of that cyclepossess an inherent disadvantage in that the equipment required tocontrol the flow of fluid and thus to achieve refrigeration by themethod and cycle described is expensive and diflicult to assemble.

It would therefore be desirable to have available a more simple,eflicient, and reliable means for controlling the valve operation ofthis type of clyogenic refrigerator and thereby supply high-pressurefluid and discharge lowpressure fluid in proper sequence to achieve therefrigeration method described in U.S.P. 2,966,035. Since therefrigerator requires a high-pressure fluid to operate on, it would alsobe desirable if the driving means were fluid actuated. The apparatus ofthis invention provides a fluidactuated driving system incorporatingvalving means which are an integral part of a refrigerator operating onthe cycle described in UB1. 2,966,035. The driving system of thisinvention can also be used with pulse-tube type refrigerators such asshown and described in U.S.P. 3,188,818.

Taking for example a small gas-operated refrigerator it may be pointedout that such a device can be operated on shop compressed air to findmany uses. Most medical and biology laboratories require small amountsof lowtemperature refrigeration for such work as the preparation oftissues for microscopic examination and the freezing of solutions.Usually, refrigeration needs are met by liquid nitrogen or solid CO Forthose requiring large quantities of continuous refrigeration, this isnot too difficult. But it is not easy to obtain just one liter of liquidnitrogen or one pound of solid CO and if a small amount of cooling isdesired continuously for weeks around the clock, it is diflicult toarrange for this using cryogenic fluids or solids. Many experiments thatrequire temperatures below 233 K. (40 C.)the nominal lower limit ofFreon refrigeration-must be performed at temperatures fixed by therefrigerant used, e.g., liquid nitrogen (about 77 K.) and solid CO(about 195 K.). Temperatures between 100 K. and 230 K. have beendifficult to realize experimentally. There is therefore a need for asmall refrigerator which requires only a source of compressed gas,whether air, helium or some other gas.

It is therefore a primary object of this invention to provide acryogenic refrigerator which incorporates a self-regulatingfluid-actuated driving system, the fluid being used as the refrigerantin the refrigerator. It is an other object of this invention to provideapparatus of the character described which is particularly suitable forperforming the cryogenic refrigeration cycle described in U.S.P.2,966,035 and 3,188,818. It is yet another object to provide a cryogenicrefrigerator which may be connected to a high-pressure fluid source andrun continuously over a long period of time without attendance ormaintenance. Other objects of the invention will in part be obvious andwill in part be apparent hereinafter.

The invention accordingly comprises the features of construction,combination of elements, and arrangement of parts which will beexemplified in the construction hereinafter set forth, and the scope ofthe invention will be indicated in the claims.

For a fuller understanding of the objects of the invention referenceshould be had to the following detailed description taken in connectionwith the accompanying drawings in which FIG. 1 is a longitudinalcross-section of the cryogenic refrigerator of this invention showingthe fluid-actuating valving system as an integral part of therefrigerator;

FIG. 2 is a cross-section of the refrigerator of FIG. 1 taken along line2--2 of that figure;

FIG. 3 is a cross-section of the valving system of FIG.

'1 showing one embodiment of a Work extracting means;

FIG. 4 is a cross-section of the valving system showing anotherembodiment of a work extracting means; and

FIGS. 5-8 are partial cross sections of the valving system and displacerillustrating the operation of the apparatus during one complete cycle.

The refrigerator of FIG. 1 comprises an external housing 10 sealed onthe bottom end by a plug 11 of a material which has high thermalcapacity at the refrigeration temperature. Within the cylindricalhousing In is a displacer 12 which reciprocates up and down to definewithin the housing a warm fluid chamber 13 and a cold or refrigeratingchamber 14. These are, of course, of variable volume, the volumed-epending upon the position of the displacer. Chambers 13 and 14 are influid communication through a fluid flow path which contains suitableheat-storage means. In the embodiment of the refrigerator shown in FIG.1, the fluid flow path comprises an axial conduit 15 which communicatesthrough the valving system between warm chamber 13 and a regenerator 16which is located within the displacer 12. The regenerator may be formedof packed lead balls 17, fine screening, of wire, or of any othersuitable heatstorage material. From the regenerator 16 the fluid floWpath continues in the form of radial passages 18 and a narrow annularpassage 19 which is defined by a smaller diameter lower section of thedisplacer and the internal walls of the refrigerator. A heat station 21is positioned around the external housing 10 in heat conductingrelationship with the cold chamber 14. Heat station 21 serves tostabilize the temperature of the cold chamber 14 and hence therefrigeration delivered at the surface of bottom end plug 11.

The fluid-actuated driving system of this invention is indicatedgenerally by the numeral 23 and it will be seen to be positioned influid-tight relationship with the refrigerator. In order to do this,external housing 10 terminates at its upper end in a threaded section 25which is adapted to be joined to a threaded base 26 of the drivingsystem. A sealing ring 27 completes the fluid-tight connection. Base 26conveniently has a flange 28 which is adapted for joining to arefrigerator support 29.

The displacer 12 has at its upper end a threaded connector piece 33which is joined to the main displacer 12 through sealing ring 34 andforms a fluid-tight seal with threaded section 25 through a sealing ring35. The refrigerator has an adaptor 38 which is arranged to permitconnecting it to a supply of compressed fluid through means not shown.Within adaptor 38 there is provided a high-pressure gas inlet 39 whichcommunicates directly into warm chamber 13 of the refrigerator. Asection 41 of the main displacer extends into the valve housing which iscompleted by a vertically extending section 42 having a removable endplug 43. A sealing ring 36 is provided to insure that chamber 13 remainsfluid tight.

The valving mechanism of this fluid-actuated driving means is indicatedgenerally by the numeral 45. It is made up of inlet poppet valves 46 (ofwhich there may be two or more) and a discharge poppet valve 47. All ofthese poppet valves are mounted on a yoke 49 which is located in a smallvalve chamber 44 within the top of the displacer. The inlet poppetvalves 46 are connected to a yoke 4-9 through valve stems 48 which passdown through ports 53 drilled in the threaded displacer connectorsection 33. As will be seen, the outlet poppet valve 47 is mounteddirectly on the yoke, and integral with it is a vertical extension 50which is terminated at the upper end in a threaded section 51 on whichis mounted a valve shifer collar 52. Associated with the valve mechanismare three springs 55, 56, and 57, the purpose of which will becomeapparent in the description of the operation of the refrigerator. Guidevanes 58, mounted on the valve extension 50, serve to position it withinthe displacer extension 41.

In FIG. 1 the paths of the high-pressure fluid and of the exhaust fluidmay be traced. The high-pressure fluid entering through inlet 39 intowarm chamber 13 passes through ports 53 into valve chamber 44 and thenceby way of conduit 15, regenerator 16, radial passages 18 and annularpassage 19 into the refrigeration chamber 14. The path of thelow-pressure exhaust fluid is the reverse of the high-pressure fluid upto the point where the exhaust fluid enters chamber 44. It then isdischarged through poppet valve 47 into an annular passage 64 which isdefined between the displacer extension 41 and the valve extension 50.The low-pressure fluid then enters chamber 65 to pass around collar 52into outlet chamber 66 and thence through throttle valve 67, the purposeof which is to modulate the flow of fluid from the system and controlthe operation of the refrigerator during the low-pressure portion of thecycle. It will, of course, be understood that the low-pressure fluid mayexhaust to the atmosphere (open cycle) or may be returned to the systemby way of suitable conduits which lead first into a compressor and theninto a high-pressure storage system (closed cycle).

FIG. 3 illustrates a modification of the fluid-actuator and includes amodified sealing system as well as means for absorbing work energydeveloped in the system. This is desirable since the combinationdisplacer-piston used (displacer 12 plus displacer extension 41)develops some mechanical energy and a work absorbing means canconveniently be employed as a form of governor to regulate the operationof the refrigerator.

In FIG. 3 two sealing-rings 70 and 71 replace the single sealing ring 35of FIG. 1 between the upper end of the displacer and the cylindricalhousing. Between the grooves in which sealing rings 70 and 71 arelocated there is provided a narrow annular passage 72 which is in fluidcommunication by way of bleed-off line 73 with the low-pressure side ofthe system. This arrangement prevents any high-pressure fluid in chamber13 from leaking into the cold voids of the refrigerator wherecontaminants can freeze and interfere with the movement of thedisplacer. This seal is the subject of my copending application Ser. No.503,726, filed Oct. 23, 1965.

Energy may be extracted from the system through the development offriction. This can conveniently be done by providing a high-pressureannular channel 76, connected to the high-pressure inlet through conduit77. An elastic band 78 seals the channel 76 and by reason of thehigh-pressure fluid acting on it, it applies pressure against suitablepressure-applying members 79 which are in frictional contact with aportion of the surface of the displacer extension 41. As this extensionmoves up and down friction is developed at these contacting surfacesthus removing energy from the system. Any other suitable means, e.g.,springs, screws, etc., may of course be used in place of tfuid pressureto maintain the members 79 in contact with the displacer extension 41.

Other minor modification included in the embodiment of FIG. 3 include anenlarged extension 80 of the valve extension 5% on which the collar 52is mounted. The lowpressure fluid path also includes ports 81 whichcommunicat-e between annular passage 64 and 82 which connect directly toan upper exhaust fluid passage 83 and an outlet 84.

FIG. 4 is a cross-sectional view of a portion of a refrigeratorconstructed in accordance with this invention showing anothermodification of an energy-absorbing means which may be associated withthe fluid-actuated valve system. As pointed out in conjunction with thedescription of FIG. 3, some work-absorbing means is desirable in therefrigerator. In FIG. 4 like reference numerals refer to like apparatuscomponents in FIGS. 1-3.

The work-absorbing means of FIG. 4 is hydraulic in character andincorporates an additional fluid chamber and piston. The piston, in itsvertical motion, does work on a fluid by moving it from one section ofchamber to another through a constriction or orifice. The fluid chamheris located above chamber 13 and in the modification shown in FIG. 4 isdefined by a lower plate 88 and an upper plate 89 which are permanentlyaflixed to the inner wall of the refrigerator housing 10. Suitablesealing means such as O-ring seals 90 and 91 are provided to permit thedisplacer extension 4 1 to move vertically within the fluid chamber 92and maintain it fluid tight. Attached to the.

displacer extension 41 is a piston 93 having an O-ring seal 94. As thedisplacer moves up and down it moves piston 93 in chamber 92 to transferfluid between subchambers 95 and 96 which are connected through aconduit 97 having an orifice 98. Thus work is absorbed in the movementof the fluid through the orifice.

The cycle of the operation of the cryogenic refrigerator is shown inFIGS. 5-8 which represent the four steps of the cycle. These steps areessentially those which are described in some detail in U.S.P.2,966,035.

In FIGS. 58 only that part of the apparatus is drawn which enters intothe operation of the refrigerator in the cycle described. The displacerin these drawings is shown as a single unit 12 and the details of theregenerator and various fluid paths which are shown in FIG. 1 have notbeen repeated. The various springs are illustrated since they enter intothe operation of the valve system. However, the details of the housingaround these springs which defines the fluid flow paths are not repeatedin these drawings. In all cases like numerals refer to like elements inall of the figures.

It is necessary in the operation of the refrigerator cycle to introducehigh-pressure, initially cooled fluid into the refrigeration chamber 14through the fluid flow path described. It is then necessary to expandthe high-pressure fluid through the system and to further cool it bycausing the exhaust valve to open, some of the fluid to discharge, andrefrigeration to be delivered to the refrigerating end plug 11 which inthis example is the point at which refrigeration is delivered to a load.

In describing the operation of the apparatus of this invention assumethat FIG. 5 represents the position of the displacer and the valvesystem at the point where the displacer 12 has reached top dead center.At this step in the cycle the refrigerating chamber 14 has attained itsmaximum volume, the discharge valve has just opened and the fluid isjust beginning to be discharged and ex= panded. It will be seen thatunder these circumstances the inlet valves 46 are closed and thedischarge valve 47 is open. This has been brought about by the fact thatcollar 52 has made contact with the valve shifter spring 55 thus forcingthe inlet poppet valves 46 to seat and the outlet valve 47 to open.High-pressure fluid entering through inlet 39 indicated in FIGS. -8 bythe arrow exerts pressure on the poppet valves 46 and maintains them ina closed position by virtue of the pressure difference which existsbetween this high-pressure fluid and the fluid pressure throughout therefrigerator. This condition of the valve system obtains throughout thatportion of the cycle which includes the downward movement of thedisplacer as indicated by the arrow in FIG. 6.

As the displacer 12 moves downwardly, the now lowpressure fluid inchamber 14 is swept out of the refrigerator as indicated by the arrow inconduit 15. Because of the high-pressure fluid in chamber 13 the inletvalves remain closed and the low-pressure fluid which gives uprefrigeration to the regenerator sweeps out of the refrigerator throughthe low-pressure fluid path consisting of passages 64, 6-5, 66 andthrottle valve 67 (see FIG. 1). The displacer is caused to movedownwardly through the action of the high-pressure fluid in chamber 13until it reaches its lowermost position. It will be seen in FIG. 7 thatat this point collar 52 contacts valve shifter spring 56 and there is apoint reached at which the upward force of the spring 56 overcomes thedownward force of the fluid pressure in chamber 13 and snaps the valvesystem upwardly to close the discharge valve 47 and open the inletvalves 46. The position of the apparatus components just subsequent tothe snap action exerted by spring 56 is shown in FIG. 7. At this pointthere is no appreciable quantity of fluid in the cold chamber 14 butwarm chamber 13 has reached its maximum volume.

At this point it is necessary to move displacer 12 up- Wardly andtransfer the warm high-pressure fluid into the refrigerating chamber 14by way of the regenerator to cool it and to deliver to chamber 14initially-cooled highpressure fluid. As the displacer 12 moves upwardly,the inlet poppet valves 46 remain open as shown in FIG. 8. The upwardmovement of the displacer is brought about by the fact that the pressureof the fluid in chamber 14 is greater than that pressure which is actingupon the displacer extension 41 which is, of course, within thelowpressure region of the refrigerator.

When the displacer 12 reaches its uppermost position then collar 52contacts valve shifter spring 55' which causes the valves to snap intothe position shown in FIG. 4-i.e., the high-pressure inlet valves 46 areclosed and the exhaust valve 47 is opened to begin the cycle at thepoint described in connection with the discussion of FIG. 4. Spring 57is included to insure that yoke 49 is always in a definite position whenthe unit is stopped. This prevents the valves from assuming anintermediate position wherein both are open, a situation which wouldprevent the unit from being self-starting.

The operation of the refrigerators of FIGS. 3 and 4 is identical to thatof FIG. 1. in addition, the annular channel 76 in the apparatus of FIG.3 is continuously maintained at high-pressure by virtue of the fact thatthe highpressure inlet is in constant fluid communication with thischannel. The high-pressure fluid in 76 continuously forces the elasticband 78 against the pressure-applying members 79 thus maintainingcontinuous contact between them and the surface of displacer extension41. The friction developed in the apparatus of FIG. 3 and the workrequired to move the hydraulic fluid in the apparatus of FIG. 4 serve aswork extracting means.

Although the refrigerator illustrated in FIG. 1 shows only a single coldchamber, it is within the scope of this invention to incorporate thedriving system shown herein in cryogenic refrigerators which areconstructed to have a stepped displacer and multiple, successivelycolder refrigeration chambers. Each segment or step of the displacer insuch a modification has a regenerator associated with it. (See forexample FIGS. 6, 9 and 10 of U.S.P. 3,218,815.) The operation of thedriving system and the cycle are the same as that described for therefrigerator of FIG. I.

The cryogenic refrigerator of this invention Will be seen to have itsdriving mechanism and valving system incorporated directly in it. Noexternal driving means or valving system are necessary since the entireoperation of the refrigerator depends only upon supplying a highpressurefluid to it. This high-pressure fluid may be shop compressed air, orcompressed nitrogen, hydrogen or helium. The fluid-actuation of allparts insures a steady coordinated operation.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efliciently attained and,since certain changes may be made in the above construction withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed, and all statements of the scope of the invention which, as amatter of language, might be said to fall therebetween.

I claim:

1. In a cryogenic refrigerator in which a high-pressure fluid isdelivered from a high-pressure chamber of variable volume with initialcooling to at least one refrigerating chamber of variable volume forsubsequent expansion and further cooling by discharge from therefrigerator, and in which said fluid is transferred through saidrefrigerator by the movement of displacer means controlled through theintroduction of high-pressure fluid and the discharge of low-pressurefluid, the improvement which comprises a fluid-actuated driving meanswhich forms an integral part of said refrigerator, said driving meanscomprising in combination (a) an auxiliary high-pressure fluid chamberof constant volume in the upper end of said displacer;

(b) a fluid-pressure responsive piston extension integral with saidupper end of said displacer and having a channel therethrough providingfluid communication between said auxiliary high-pressure fluid chamberand the low-pressure region of said refrigerator;

(c) high-pressure inlet ports communicating between said high-pressurechamber and said auxiliary highpressure chamber; and

(d) pressure-responsive, valve means associated with said inlet portsand said channel and adapted to close said inlet ports and open saidchannel during that portion of the refrigeration cycle when saidrefrigerating chamber attains maximum volume and is thereafterdecreasing in volume and to open said inlet ports and close said channelduring that portion of the refrigeration cycle when said high-pressurefluid chamber attains maximum volume and is thereafter decreasing involume.

2. A refrigerator in accordance with claim 1 wherein said valve meanscomprises (a) a yoke;

(b) inlet poppet valves mounted on said yoke;

(c) a discharge poppet valve mounted on said yoke;

(d) a valve extension located within said channel and terminatingthereabove in a collar; and

(e) spring means associated with said collar and being adapted to applysufficient pressure to said valve means to overcome fluid pressureapplied thereto thereby to effect snap action of said valve means whensaid displacer reaches its lowermost and uppermost positions.

3. A refrigerator in accordance with claim 1 further characterized byhaving work extracting means associated with said piston extension.

4. A refrigerator in accordance with claim 3 wherein said workextraction means comprises pressure-applying means in frictiondeveloping contact with said piston extension.

5. A refrigerator in accordance with claim 3 wherein said workextraction means comprises a fluid chamber, a piston afiixed to saidpiston extension movable within said chamber to define two subchambersand a fluid conduit having an orifice providing a fluid communicationbetween said subchambers.

References Cited UNITED STATES PATENTS 3,188,821 1/1965 Chellis 62-6WILLIAM J. WYE, Primary Examiner.

1. IN A CRYOGENIC REFRIGERATOR IN WHICH A HIGH-PRESSURE FLUID ISDELIVERED FROM A HIGH-PRESSURE CHAMBER OF VARIABLE VOLUME WITH INITIALCOOLING TO AT LEAST ONE REFRIGERATING CHAMBER OF VARIABLE VOLUME FORSUBSEQUENT EXPANSION AND FURTHER COOLING BY DISCHARGE FROM THEREFRIGERATOR, AND IN WHICH SAID FLUID IS TRANSFERRED THROUGH SAIDREFRIGERATOR BY THE MOVEMENT OF DISPLACER MEANS CONTROLLED THROUGH THEINTRODUCTION OF HIGH-PRESSURE FLUID AND THE DISCHARGE OF LOW-PRESSUREFLUID, THE IMPROVEMENT WHICH COMPRISES A FLUID-ACTUATED DRIVING MEANSWHICH FORMS AN INTEGRAL PART OF SAID REFRIGERATOR, SAID DRIVING MEANSCOMPRISING IN COMBINATION (A) AN AUXILIARY HIGH-PRESSURE FLUID CHAMBEROF CONSTANT VOLUME IN THE UPPER END OF SAID DISPLACER; (B) AFLUID-PRESSURE RESPONSIVE PISTON EXTENSION INTEGRAL WITH SAID UPPER ENDOF SAID DISPLACER AND HAVING A CHANNEL THERETHROUGH PROVIDING FLUIDCOMMUNICATION BETWEEN SAID AUXILIARY HIGH-PRESSURE FLUID CHAMBER AND THELOW-PRESSURE REGION OF SAID REFRIGERATOR; (C) HIGH-PRESSURE INLET PORTSCOMMUNICATING BETWEEN SAID HIGH-PRESSURE CHAMBER AND SAID AUXILIARYHIGHPRESSURE CHAMBER; AND (D) PRESSURE-RESPONSIVE, VALVE MEANSASSOCIATED WITH SAID INLET PORTS AND SAID CHANNEL AND ADAPTED TO CLOSESAID INLET PORTS AND OPEN SAID CHANNEL DURING THAT PORTION OF THEREFRIGERATION CYCLE WHEN SAID REFRIGERATING CHAMBER ATTAINS MAXIMUMVOLUME AND IS THEREAFTER DECREASING IN VOLUME AND TO OPEN SAID INLETPORTS AND CLOSE SAID CHANNEL DURING THAT PORTION OF THE REFRIGERATIONCYCLE WHEN SAID HIGH-PRESSURE FLUID CHAMBER ATTAINS MAXIMUM VOLUME ANDIS THEREAFTER DECREASING IN VOLUME.